F1 Fast Version® genetics: discovery, breeding and advantages

Manolo, who works for Sweet Seeds®, explains how the different strains of F1 Fast Version® were discovered and their advantages.

Cannabis plants follow one of two flowering patterns. Classic strains are photoperiod-dependent, that is, they start flowering when the number of hours of daylight declines. Autoflowering strains , on the other hand, flower according to their age, regardless of the photoperiod. F1 Fast Version® strains are photoperiod-dependent; however, they have some autoflowering genetics which are not fully expressed but which do contribute to an early harvest.

F1 Fast Version® and Mendel’s laws of inheritance

F1 hybrids, also known as commercial seeds, are created by crossing two different pure lines. The main characteristics of F1 hybrids are the uniform nature of their properties and the phenomenon called hybrid vigour. According to Mendel’s first law, the offspring of the first filial generation (F1) will be uniform and very similar to the parent carrying the dominant allele. Mendel’s second law states that the offspring in the second filial generation (F2), obtained by crossing individuals from the first generation, will bear a 50% similarity to the first filial generation genotype, 25% dominant genotype and 25% recessive genotype. Mendel’s third law asserts the rule of independent transmission of inherited characteristics, in other words, the inheritance of one trait bears no influence on the inheritance of another trait.

F1 Fast Version® lines fulfil all three rules, they display typical Mendelian inheritance, given that the type of flowering is determined by just a single gene. Autoflowering lines contain two alleles of the autoflowering trait, which is recessive – this means the trait is only expressed (occurs) when two alleles that transmit autoflowering combine. Photoperiod-dependent lines contain two alleles of the dominant photoperiod-dependent flowering trait. The only exception are plants with F1 Fast Version® genetics, which contain a dominant allele that transmits photoperiod-dependence to all offspring and a recessive allele that transmits, but does not express, autoflowering.

This is because F1 Fast Version® strains are produced by combining a photoperiod-dependent parent with an autoflowering parent. As Mendel’s first law stipulates, all offspring are uniform and closely resemble the dominant parent, which is why all descendants express the photodependence trait even though they contain both traits. The presence of the autoflowering allele is not expressed in the phenotype (external appearance), but it does contribute by accelerating maturation and flowering. When two F1 Fast Versions® are crossed, they produce offspring in proportions of 50% F1 Fast Version®, 25% autoflowering and 25% regular photoperiod-dependent plants. Therefore, when breeding an F1 Fast Version® line, you must always combine a photoperiod-dependent plant with an autoflowering one and only the first generation from this cross will be F1 Fast Version®.

There are many different types of autoflowering strains. Some have a long flowering period, but they are not very interesting for growers because they take just as long to grow as photoperiod-dependent strains. The most popular autoflowering plants start their 5 week flowering period just 21–28 days after germination, which means they are ready to harvest in a total of 8–9 weeks. This rapid growth pattern is transmitted to the offspring in F1 Fast Version® lines, resulting in slower flowering than autoflowering plants, but quicker than photoperiod-dependent examples.

Autoflowering breeding

Sweet Seeds® started working on autoflowering genetics in 2007 and launched their first autoflowering strain in 2009. Besides Joint Doctor’s classic Lowryder, Sweet Seeds® used other genetic lines, most notably some early creations by Lowlife Seeds or several lines from northern USA and Canada, probably crosses derived from Ernest Small or Mighty Mite from British Columbia.

There is no explanation of the autoflowering phenomenon in the scientific literature, but after analysing the trait’s inheritance and conducting various experiments, scientists reached the conclusion that the autoflowering trait is transmitted by a single gene, possibly a defective photoperiod-dependent gene that may have persisted in the cannabis gene pool since ancient times.

This mutation is beneficial in cold climates, where wild cannabis plants must complete flowering and produce viable seeds before autumn arrives. In the past, a lot of hemp was grown in regions such as northern USA and Canada, which both have harsh climates, but the crops were abandoned for various reasons. Once these domesticated strains were allowed to evolve naturally and unrestricted in the wild, the gene could start expressing itself again. Whenever this occurs, it represents an adaptive advantage for plants with the autoflowering trait growing in a cold climate.

Sweet Seeds® soon realised that these genotypes, which were unpopular due to their taste or size, actually had great potential but just required genetic improvement and optimisation. So, they set about improving these primitive autoflowering plants by crossing them with their favourite elite clones.

After checking the results of crossing the autoflowering genotypes with their photoperiod-dependent elite clones, Sweet Seeds® confirmed there wasn’t a single autoflowering plant in the first generation, as predicted by Mendel’s first law, as all offspring where uniform and akin to the dominant photoperiod-dependent parent. As such, in accordance with Mendel’s second law, they had to wait for the next generation before genotype segregation occurred, wherein 25% of the offspring were autoflowering. Crossing these autoflowering, second-generation individuals with each other subsequently yielded an entire generation of plants expressing the autoflowering trait. Mendel’s third law states the independence of inherited characteristics; so not only is autoflowering now a stable trait of the third-generation offspring, but they can also incorporate flavours and psychoactive properties inherited from the photoperiod-dependent parental line. Therefore, this technique produces strains of increasingly higher quality while retaining the autoflowering trait.

Discovery and breeding of F1 Fast Version®

During early experiments with autoflowering plants, while developing Cream Caramel Auto®, Manolo noticed that the first generation did not express the autoflowering trait, but they did present a shorter flowering period. Initially, he checked the dates he had marked in the calendar to confirm it wasn’t due to a data recording error. He tried again and got the same result: the plants required less time to flower. Now he was convinced of this great new property in the first generation of plants crossed from photoperiod-dependent and autoflowering plants. After creating Cream Caramel Auto®, Sweet Seeds® started to work along the same lines with other strains and observed the same results. At this point they decided to incorporate F1 Fast Version® strains into their catalogue and even registered the name as a trademark.

F1 Fast Version® strains are F1 hybrids, they are always the first generation produced by crossing a photoperiod-dependent genotype with an autoflowering individual. The parents of autoflowering plants cannot be kept in the form of clones, so they always enjoy constant improvement, since if the correct selection and breeding process is applied to each generation, the strain will evolve depending on which parents were selected. That is why F1 Fast Version® strains are always undergoing continuous development that is linked to the advances made in the autoflowering parent. When the autoflowering line benefits from a correct selection process, the F1 Fast Version® line will also improve.

In fact, F1 Fast Version® strains provide a rapid means of breeding and enhancing elite clones. The technique produces clone versions that flower earlier, present increased hybrid vigour and facilitate the selection of other desirable characteristics.

Manolo went on to explain that, besides their own breeding projects, Sweet Seeds® has also been collaborating with an official plant biotechnology organisation. This line of research has involved many years of work and significant financial investment, but research always entails a certain degree of luck, because there is no guarantee of achieving the proposed objectives when making the initial investment.

Advantages of F1 Fast Version® strains

Shorter flowering is reinforced with each generation crossed from the ancestor auto, as we select the best individuals from each family as parents, with particular emphasis on those that flower quickly, a trait that they transmit to their descendants. Thanks to this rapid harvest, growers can avoid the fungal problems associated with damp, rainy autumn weather.

In addition to a shorter flowering period, F1 Fast Version® strains display the typical hybrid vigour of F1 hybrids, as demonstrated by, for example, Green Poison F1 Fast Version®, a strain with even greater yields and potency than the classic photoperiod-dependent version, and which can also be harvested outdoors at the beginning of September or even the end of August. Green Poison F1 Fast Version® is a very fast Skunk, it is ready after just 6–7 weeks of flowering, but it is also easy to grow and provides excellent yields with resinous buds and an intense aroma.

Another advantage of F1 Fast Version® strains, since they are photoperiod-dependent, is that you can take cuttings of your favourite plant to save as a mother plant, whereas autoflowering strains can only be grown from seeds. Growers can plan the height and yield with these strains. If you want large plants, just start earlier in the year to give them a longer growing period; alternatively, for indoor cultivation, stick to the growth photoperiod schedule until the plants reach the desired height.


According to Manolo, the launch of the F1 Fast Version® strains has been a great success, “when I discovered them, I realised they present a lot of advantages for growers. I thought they could change things, but I wasn’t sure if our customers would like them. Although we didn’t see an explosion in demand like when we launched our autoflowering lines, interest from customers is growing steadily each year. As the saying goes, ‘time is precious, invaluable’. Those who have tried them are satisfied and choose to plant them again. Other seed banks have even started offering similar fast lines. We have expanded our F1 Fast Version® family to include 14 strains F1 Fast Version® and we are already preparing some more new strains for release this year. I think the introduction of the F1 Fast Version® line has been very positive, we have diversified our catalogue of genotypes and above all we offer something our customers value, a shorter flowering period, which is evidenced by the fact that they grow them again year after year. First and foremost, they are very useful strains for growers aiming for a shorter harvest because they live in cold or damp climates. In any case, they give excellent results in all climates. Growers in hot regions also opt for F1 Fast Version® seeds so they can harvest and enjoy their plants earlier, besides benefiting from the line’s hybrid vigour making them ideal for both indoor and outdoor growing.”

Sweet Seeds S.L is not responsible for the misuse of the information contained in this article. Cultivation of cannabis may constitute a criminal offence or administrative misdemeanour; please refer to the legislation on cannabis in your place of residence. Sweet Seeds S.L. does not intend in any case to incite non-legal practices.


Texto: @Sweet Seeds®